// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Whole-tree processing that's likely to be helpful in multiple render models.

#include "gpu/tools/compositor_model_bench/render_model_utils.h"

#include <cstdlib>
#include <map>
#include <set>
#include <vector>

#include "base/logging.h"

TextureGenerator::TextureGenerator(RenderNode* root)
    : stage_(DiscoveryStage)
    , images_generated_(0)
{
    DiscoverInputIDs(root);
    GenerateGLTexIDs();
    AssignIDMapping();
    WriteOutNewIDs(root);
    AllocateImageArray();
    BuildTextureImages(root);
}

TextureGenerator::~TextureGenerator()
{
    if (tex_ids_.get()) {
        glDeleteTextures(discovered_ids_.size(), tex_ids_.get());
    }
}

void TextureGenerator::BeginVisitRenderNode(RenderNode* node)
{
    for (size_t n = 0; n < node->num_tiles(); ++n) {
        Tile* i = node->tile(n);
        HandleTexture(&i->texID,
            node->tile_width(),
            node->tile_height(),
            GL_RGBA);
    }
}

void TextureGenerator::BeginVisitCCNode(CCNode* node)
{
    for (size_t n = 0; n < node->num_textures(); ++n) {
        Texture* i = node->texture(n);
        HandleTexture(&i->texID, i->width, i->height, i->format);
    }
    BeginVisitRenderNode(node);
}

void TextureGenerator::DiscoverInputIDs(RenderNode* root)
{
    // Pass 1: see which texture ID's have been used.
    stage_ = DiscoveryStage;
    root->Accept(this);
}

void TextureGenerator::GenerateGLTexIDs()
{
    int numTextures = discovered_ids_.size();
    tex_ids_.reset(new GLuint[numTextures]);
    glGenTextures(numTextures, tex_ids_.get());
}

void TextureGenerator::AssignIDMapping()
{
    // In the original version of this code the assigned ID's were not
    // GL tex ID's, but newly generated consecutive ID's that indexed
    // into an array of GL tex ID's. There's no need for this and now
    // I'm instead generating the GL tex ID's upfront and assigning
    // *those* in the remapping -- this more accurately reflects the
    // behavior in Chromium, and it also takes out some design
    // complexity that came from the extra layer of indirection.
    // HOWEVER -- when I was assigning my own ID's before, I did some
    // clever tricks to make sure the assignation was idempotent.
    // Instead of going to even more clever lengths to preserve that
    // property, I now just assume that the visitor will encounter each
    // node (and consequently each texture) exactly once during a
    // traversal of the tree -- this shouldn't be a hard guarantee
    // to make.
    int j = 0;
    typedef std::set<int>::iterator id_itr;
    for (id_itr i = discovered_ids_.begin();
         i != discovered_ids_.end();
         ++i, ++j) {
        remapped_ids_[*i] = tex_ids_[j];
    }
}

void TextureGenerator::WriteOutNewIDs(RenderNode* root)
{
    // Pass 2: write the new texture ID's back into the texture objects.
    stage_ = RemappingStage;
    root->Accept(this);
}

void TextureGenerator::AllocateImageArray()
{
    image_data_.reset(new ImagePtr[discovered_ids_.size()]);
    images_generated_ = 0;
}

void TextureGenerator::BuildTextureImages(RenderNode* root)
{
    // Pass 3: use the texture metadata to generate images for the
    // textures, and set up the textures for use by OpenGL. This
    // doesn't *have* to be a separate pass (it could be rolled
    // into pass 2) but I think this is more clear and performance
    // shouldn't be bad.
    stage_ = ImageGenerationStage;
    root->Accept(this);
}

void TextureGenerator::HandleTexture(int* texID,
    int width,
    int height,
    GLenum format)
{
    if (*texID == -1)
        return; // -1 means it's not a real texture.
    switch (stage_) {
    case DiscoveryStage:
        discovered_ids_.insert(*texID);
        break;
    case RemappingStage:
        *texID = remapped_ids_[*texID];
        break;
    case ImageGenerationStage:
        // Only handle this one if we haven't already built a
        // texture for its ID.
        if (ids_for_completed_textures_.count(*texID))
            return;
        GenerateImageForTexture(*texID, width, height, format);
        ids_for_completed_textures_.insert(*texID);
        break;
    }
}

void TextureGenerator::GenerateImageForTexture(int texID,
    int width,
    int height,
    GLenum format)
{
    int bytes_per_pixel = FormatBytesPerPixel(format);
    DCHECK_LE(bytes_per_pixel, 4);
    int imgID = images_generated_++;
    image_data_[imgID].reset(new uint8[width * height * bytes_per_pixel]);
    // Pick random colors to use for this texture.
    uint8 random_color[4];
    for (int c = 0; c < 4; ++c) {
        random_color[c] = std::rand() % 255;
    }
    // Create the image from those colors.
    for (int x = 0; x < width; ++x) {
        for (int y = 0; y < height; ++y) {
            int pix_addr = (y * width + x) * bytes_per_pixel;
            for (int c = 0; c < bytes_per_pixel; ++c) {
                bool on = ((x / 8) + (y / 8)) % 2;
                uint8 v = on ? random_color[c] : ~random_color[c];
                (image_data_[imgID])[pix_addr + c] = v;
            }
            if (bytes_per_pixel == 4) { // Randomize alpha.
                image_data_[imgID][pix_addr + 3] = std::rand() % 255;
            }
        }
    }
    // Set up GL texture.
    glBindTexture(GL_TEXTURE_2D, texID);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glPixelStorei(GL_PACK_ALIGNMENT, 1);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glTexImage2D(GL_TEXTURE_2D,
        0,
        format,
        width, height,
        0,
        format,
        GL_UNSIGNED_BYTE,
        image_data_[imgID].get());
}
